Subscribe To VT Ichthyology

Friday, May 11, 2018

What Limits Recovery of Atlantic Sturgeon, Austin Beaudet

One hundred years ago, a fisherman could fish in any river
on the east coast and have a chance to catch a colossal, prehistoric looking
monster, Acipenser oxyrinchus, or
better known as the Atlantic Sturgeon. This bony plated monster could grow up
to 14 feet in length a weigh a whopping 800 pounds (NOAA). This creature’s huge
size and bizarre features made it a target to fisherman all along the east
coast. They began to catch these fish at an at a frantic pace to get in on the
short lived goldmine that sturgeon provided. Then it all just stopped. Humans
kept hunting them until they had completely decimated their numbers. In areas
like the Chesapeake Bay which had an estimated 20,000 sturgeon at one point
were brought down to roughly 300 alive in the present that are able to
reproduce (Dietrich 2017). Since the inclusion of the sturgeon under the
endangered species act, many groups and agencies have been desperately trying
to bring this population back to a much more stable and healthy size. Certain
methods of recovery today include a ban on all capture of Atlantic Sturgeon,
hatcheries attempting to provide a boost to the sturgeon population, and other
research projects and studies which are trying to learn more about the habitat,
life history, and migration patterns of the sturgeon. However, recovery efforts
are not going nearly as well as we have hoped and the sturgeon population has
failed to comeback in the numbers we wished and many people want to figure out
why. According to the research and data that scientists currently have, the
main problems limiting the recovery efforts are bycatch mortality, water
quality, and dredging activities which all seem to be hugely detrimental in
regions inhabited by sturgeon.

Water quality plays a major role in the development,
reproduction, and overall health of the Atlantic Sturgeon. Although there has
been multiple laws protecting our waters from pollution, mankind still finds a
way to dump harmful chemicals into our river system. One chemical that is
particularly damaging to the recovery of sturgeon is polychlorinated biphenyls
(PCB). PCB was a very popular form of coolant within many electrical systems in
the 1900’s but usage has since declined due to the discovery of it's harmful properties
to both humans and wildlife. However, the damage has already been done and will
continue to haunt our environment long into the foreseeable future. One
estimate has stated that the United States has produced 600,000 tonnes of PCB
and a good portion of it has entered our riverways (Cooper 1989, Sinderman
1994). To make things worse, according to the Atlantic Sturgeon Status Review,
“Atlantic sturgeon may be particularly susceptible to impacts from
environmental contamination due to their benthic foraging behavior and
long-life span” (Cooper 1989, Sinderman 1994). Today, PCB sits at the bottom of
local rivers and continues to poison the sturgeon population and it seems as
though there is very little we can do about it. Studies have now been conducted
and have concluded that, “exposure to PCBs reportedly causes a higher incidence
of fin erosion, epidermal lesions, blood anemia, and an altered immune
response” (Kennish et al. 1992). Until a proper method of removal of PCB from
our waterways can be figured out then sturgeon will never stop dealing with the
consequences the pollutant causes.

Another major factor that continues to hinder Atlantic
Sturgeon recovery efforts is the freshwater dredging that occurs up and down
the east coast river systems. This dredging still goes on today and it needs to
be run in a much more environmentally conscious manner or be shut down all
together. The consequences that sturgeon face due to dredging include, “direct
removal/burial of organisms; turbidity/siltation effects; contaminant
resuspension; noise/disturbance; alterations to hydrodynamic regime and
physical habitat and actual loss of riparian habitat...destruction of benthic
feeding areas, disruption of spawning migrations, deposition of resuspended
fine sediments in spawning habitat…, and the lethal entrainment of fish up
through the dredge drag-arms and impeller pumps” (Chytalo 1996, Winger et al.
2000). To make matters worse, this form of dredging is not nearly regulated
enough especially considering the damage is currently is causing. Changes need
to start happening as soon as possible if there is still hope to save the
Atlantic Sturgeon population from extinction.

A five-foot Atlantic Sturgeon killed by ship strike in the James River, Virginia. Photo by James River Association. creative commons Flickr

The last major factor preventing the Atlantic Sturgeon from
having a stable population size is the damages done through ship strikes and
by-catch of the sturgeon (Melnychuk et al. 2016; ASMFC 2017). By-catch is when a certain fish is caught by
commercial fisheries that is not the intended target fish. Although intentional
hunting of Atlantic Sturgeon is strictly banned, bycatch still remains to be a
huge problem. Records show that Atlantic Sturgeon become victims of by-catch
through trawls, pound nets, and gill nets. Pound nets seem to be the least
damaging to the sturgeon population and don’t have any recorded cases of
directly causing death to sturgeon. Trawls have caused some deaths in the
sturgeon population but most trawling systems on the southern half of the east
coast have mechanisms in place to help prevent the capture of unwanted fish
species. Gill nets are the main source of death and accountable for doing the
most harm to the sturgeon population. Certain surveys have shown that sturgeon
caught in these nets have up to a 70% chance of mortality depending on length
of time before the sturgeon are freed (NMFS Observer Database). These nets
continue to cause incidents that result in the death of sturgeon every year and
if environmental groups and protection/conservation agencies continue to work
on the recovery of this species without figuring out a solution to by-catch
problems then their fight will most likely be doomed.

When thinking of limiting factors to the
recovery of the Atlantic Sturgeon, things like hunting, global warming, and
fecundity come to mind. However, after extensive research it can clearly be
seen that the obstacles limiting the Atlantic Sturgeon are quite different. Problems
dealing with water quality, by-catch, ship strikcs, and dredging all have
become major contributors in the continued decline of this species. Although
these threats may not cause as much mortality to sturgeon as ship strikes or dams
that block migration routes, they are currently problems that have gone under
the radar and need to be fixed just as badly as other, more commonly discussed
problems. The good news is that in some rivers, such as the Hudson and Savannah,biologists are beginning to see an increase
in the numbers (Bahr and Peterson 2016; New York State Conservationist 2016). If protective measures continue, the Atlantic
Sturgeon may show signs of recovery in more rivers.